Fluid phase fractions are determined using a fluid fractional composition measuring apparatus. A known apparatus comprises a radiation source and detector, wherein the radiation source is a chemical isotope radiation source. The chemical isotope radiation source may be deployed for long periods of time in unattended locations that may encounter variable ambient environmental conditions. As a consequence, there exists a security and environmental risks. Thus, there is a need to use non-chemical radiation sources for fluid fractional composition measuring apparatuses.
An x-rays generator is an electrical radiation generator alleviating some of the foregoing drawbacks. However, such an x-rays generator is subject to voltage and beam current fluctuation. As a consequence, the radiation output also fluctuates. This affects the degree of accuracy of the fluid fractional composition measurements. Thus, there is a need to control the x-rays generator, in particular, the input voltage and target current of the x-rays generator.
U.S. Pat. No. 7,684,540 describes an apparatus and method for determining the phase fraction of a fluid collected downhole comprising an x-ray generator, a filter, a sample cell, and a radiation detector. The filter produces a radiation spectrum with a high energy portion and a low energy portion. Filtered radiation is passed through a sample fluid and the resulting attenuated radiation signal is used in calculating the phase fractions of oil, water, and gas in the sample fluid. A second reference radiation detector measures the radiation directly from the x-ray generator and this measurement is used in normalizing the fraction result. The ratio of the high energy signal to low energy signal of the reference detector is used in controlling the input voltage of the x-ray generator thus ensuring a stable spectrum.
Such an apparatus requires two detectors, namely a measurement detector for measuring the attenuated radiation and a reference detector for controlling the x-ray generator and ensuring a stable spectrum. There is a need to reduce the complexity and the cost of the apparatus for fluid phase fraction determination using x-rays. Further, there is also a need to expand the operational range of the apparatus for fluid phase fraction determination using x-rays.